| This paper focuses on the study of different type of multilayer microstrip array antennas. Several novel shaped-beam multilayer microstrip arrays are proposed and studied. Good array performances are achieved. The contents of the paper list as follows:Firstly, the studies on the shaped-beam pattern synthesis method based on particle swarm optimization and the Buckley synthesis method for traveling-wave arrays are carried out. A general design method of traveling-wave arrays based on conventional traveling-wave array models is studied. A concept of active coupling coefficient is proposed to characterize the impact of the mutual coupling between the elements in a traveling-wave array on their radiating abilities. Based on this concept, an optimization method of traveling-wave arrays, which efficiently considers the mutual coupling effect between the elements, is presented.Secondly, the matching principle of a microstrip aperture-coupled stacked patch(ASP) antenna is analysed, and a parameter study of the ASP antenna is carried out. Based on a facile design of the coporate feed network, a broadband microstrip ASP antenna array with a 45 ° polarized radiation character is achieved. The measured results show that, the array has obtained a good impedance match and stable radiation patterns over a 40% bandwidth.Thirdly, a shaped-beam nonuniformly spaced series-fed microstrip aperture-coupled patch(ACP) traveling-wave array is designed and fabricated. The optimization process of the array is detailed analyzed. Good measured shaped-beam patterns are obtained, which verifiy the efficiency of the proposed traveling-wave array optimization method that considers mutual coupling effect.Fourthly, to broaden the pattern bandwidth of the shaped-beam microstrip ACP array, a novel shaped-beam uniformly spaced series-fed microstrip ASP traveling-wave array is proposed. A broadband microstrip 2-port ASP antenna is proposed as the array elements, which broadens the array’s pattern bandwidth. Besides, a uniformly spaced configuration is applied to offer more flexibility in the design and optimization processes of the array’s radiation pattern. Moreover, it ensures the synthesized shaped-beam patterns can be achieved without deviation. The fabricatied microstrip ASP array obtains good shaped beam pattern performances in a bandwidth of 7.6%.Fifthly, to decease the overall thicknesses and weights of the shaped-beam microstrip ACP and ASP arrays caused by the inevitable metal cavitis, and to overcome the loss problem within the uniformly spaced microstrip ASP array caused by the spurious radiation of the microstrip bends, a novel shaped-beam uniformly spaced stripline-fed ASP traveling-wave array is proposed. A broadband stripline-fed 2-port ASP antenna is proposed as the array elements. A simple and efficient procedure without increasing the substrate thickness is proposed to improve the stripline elements’ coupling coefficients. The experimental results of the linear array show that, its 2:1 VSWR bandwidth reaches about 33.2%. In a 3.8% frequency band, the main beam shape of the array only gets a ±1.5dB ripple, compared with the ideal beam shape, and the side lobe level maintains lower than-16 dB. Compared with the simulated directivities, the measured gains only decrease by about 0.6~1dB, which reveals the efficiency of the proposed stripline array.Sixthly, a novel multilayer shaped-beam traveling-wave slot array based on substrate integrated waveguide(SIW) is proposed. A novel SIW multilayer slot antenna is proposed as the array element, which features an improved bandwidth performance due to its double-resonant property. The double-resonant principle of the multilayer slot antenna is detailed analyzed, and a parameter study is carried out. By using this kind of slots, a linear and a planar nonuniformly spaced shaped-beam traveling-wave array is constructed. To achieve the desired distribution for the shaped-beam pattern, the optimization process of the array is detailed analyzed. The experimental results show that, the 2:1 VSWR bandwidth of the SIW linear and planar arrays is about 7.9% and 6.7%, respectively. And in a 4.8% frequency band, the SIW planar array shows good measured shaped beam pattern performances: its main beam shape maintains in good agreement with the design goal and its side lobe level maintains lower than-20 dB, which is only 2dB higher than the simulated result. Additionally, despite the loss caused by the microstrip-SIW transition, the measured gain is only 0.5dB lower than the simulated directivity at the center frequency point, which reveals the low loss feature of the proposed SIW array.Lastly, the waveguide longitudinal slot coupled microstrip array is designed and the isolation problems of this kind of arrays are studied. The measured pattern results of the array show that, at the center frequency point, the side lobe level at H plane is below-21 dB, and at E plane it is below-18.7dB, and a radiation efficiency of 62.8% is achieved. Then, based on electromagnetic band-gap(EBG) structures, an experimental study of improving isolation between the arrays is carried out. For the first time, the isolation principles and performances of the EBG walls and the hybrid choke+ EBG walls structure is experimentally analyzed. The measured results show that, the isolation between two waveguide longitudinal slot coupled microstrip arrays which loaded by the hybrid choke+ EBG walls is 30 dB higher than the isolation of these arrays without loading any isolation structures.
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